Ladder mounting for hillside combines



Dec. 8, 1964 J. c. BOONE 3,160,423

LADDER MOUNTING FOR HILLSIDE COMBINES Filed Oct. 3, 1961 3 Sheets-Sheet l Dec. 8, 1964 J. c. BOONE ,160, 3

11 LADDER MOUNTING FOR HILLSIDE COMBINES Filed Oct. 5. 1961 s Sheets-Sheet 2 Sum/ ,Q. $500M 49 @kkoPme y Dec. 8, 1964 J. c. BOONE 3,160,423

LADDER MOUNTING FOR HILLSIDE COMBINEIS Filed Oct. 5. 1961 s Sheets-Sheet s EMMA JAR/1 ,8. 63mm:

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United States Patent 3,168,423 LADDER MOUNTING FOR HILLSIDE COMBINES Jerry C. Boone, Independence, Mm, assigner to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Oct. 3, 1961, Ser. No. 142,705 13 Claims. (Cl. 280165) The invention relates to agricultural machines and it is concerned more particularly with an access ladder arrangement for hillside combines and similar vehicles.

In order to provide access to the operators station of a hillside combine, it has heretofore been suggested to divide the usual rigid ladder assembly at the mounting side of the machine into a fixed upper part which extends outwardly from the operators platform and over an underlying up and down movable drive wheel, and into a lower swingable part at the outer side of the drive wheel. Such a two part ladder arrangement is shown, for instance, in US. Patent 2,967,584, granted on January 10, 1961, to P. H. Westerlund for Ladder for Agricultural Vehicle.

For practical reasons it is desirable that the operator of a hillside combine be able to ascend to or descend from the operators platform conveniently at all times and under all terrain conditions. More particularly, the bottom end of the ladder should always remain spaced a relatively short distance from the ground at the mounting side of the combine, irrespective of any uphill or downhill slope of the ground.

The hereinabove mentioned two part ladder arrangement of the prior art has the advantage of protecting the ladder against damage which may result from contact of the lower ladder end with the ground during hillside operation. Such protection is afforded by adjustment of the lower swingable ladder section into an upwardly tilted position during hillside operation, and it is necessary to lower the swingable ladder section from its up wardly tilted position into a generally vertical position before it can be used by an operator in ascending to or descending from the operators platform. In this respect the mentioned prior art arrangement has been unsatisfactory because it does not afford convenient access to the platform at all times and under all terrain conditions.

Generally, it is an object of the present invention to provide an improved access ladder arrangement for vehicles of the hillside combine type which avoids the mentioned shortcoming of the prior art and which affords convenient access to an operatorls platform at all times and under all terrain condition in a practical and entirely satisfactory manner.

More particularly, it is an object of the invention to provide an articulated ladder arrangement which presents the lower ladder end at a proper distance from the ground under various terrain conditions so that the first or lowest step of the ladder will always be within easy reach of an operator not only from level ground, but also from uphill or downhill sloping ground at the mounting side of the machine.

A further object of the invention is to provide an improved articulated ladder arrangement of the hereinabove mentioned character which is automatically adjusted to difierent conditions as required for convenient access from level or sloping ground at the mounting side of the machine.

A further object of the invention is to provide an automatically adjusted ladder arrangement of the mentioned character which is controlled by up and down movements of a ground engaging supporting wheel at the mounting side of the machine.

A still further object of the invention is to provide an improved vehicle of the hillside combine type which has an up and down movable access ladder at the axially outer side of an up and down movable ground engaging supporting wheel, and wherein up and down movement of the ladder is controlled by up and down movement of the wheel in such a manner that the ladder will be raised and lowered relative to the wheel upon up and down movements, respectively, of the wheel relative to the vehicle body.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the description herein of an embodiment of the invention, and will be set forth in the appended claims. a

Referring to the accompanying drawings: FIG. 1 is a schematic side elevation of a hillside combine;

FIG. 2 is a front elevational view of the combine shown in FIG. 1 with the header omitted and the forward part of a thresher housing broken away and shown in section;

FIG. 3 is an enlarged side view of parts at the mounting side of the combine shown in FIG. 1, the view of FIG. 3 being taken in section on line IIIIII of FIG. 2;

FIG. 4 is an enlarged section on line IVIV of FIG. 2;

FIG. 5 is an enlarged top view of parts at the mounting side of thecombine shown in FIG. 1, the view of FIG. 5 being taken in section on line VV of FIG. 2;

FIG. 6 is an enlarged detail view of parts shown in FIG. 3;

FIG. 7 is an enlarged section on line VIIVII of FIG. 2; and

FIGS. 8 and 9 are elevational views similar to FIG. 2, but drawn on a reduced scale and showing an access ladder at the mounting side of the combine in different conditions of adjustment, railing parts shown in FIG. 2 being broken away in FIG. 8 to expose similar railing parts which are hidden in FIG. 2.

In FIG. 1 conventional components of a hillside com:

bine are shown in general outline and include a header 1, thresher housing 2, swivel joint 3 between the header and thresher housing, separator housing 4, vehicle frame 6, operators station 7, grain bin 8 and engine 9. Con ventional components and accessories such as a header reel, header tilting mechanism, straw spreader, and bin unloader have been omitted in FIG. 1 for the sake of clarity and simplification.

The forward end of the vehicle frame 6 is supported on a pair of transversely spaced power driven propelling .wheels 11 and 12 as shown in FIG. 2, and the rear end of the vehicle frame 6 is supported on a transversely rockable and steerable rear support of conventional construction which is generally designated in FIGfl by the.

reference character 13. i

Referring to FIG. 2, a tubular axle beam 14 is rockably mounted at its center on a depending bracket struc and 27 extend inwardly toward a vertical plane which extends-longitudinally of the vehicle through the axis of the pivot joint 17, and the relatively adjacent ends of the guide links 24 and 27 are hingedly connected together by means of a pivot pin 28 which is mounted on the bracket structure 16 above the pivot joint 17.

As shown in FIG. 2 the wheels 11 and, 12 are rotat-' ably mounted on the wheel carriers 21 and 22, respectively. Power transmitting gearing, not shown, for driv-' transmitting gearing enclosed within a hub structure 31. I

The mechanism for transmitting power fromthe engine 9 to the wheels 11 and 12 is of conventional construction and requires no detailed description for an understa nd-.v ing ofthe present invention.

In order -to control lateral tilting of the main body of the combine about the axis of the pivot joint 17 a stabilizing mechanism including a pair of hydraulic cylinders 32 and 33 is operatively interposed between the main body and the axle beam 14 as shown in FIGS. 2, 8 and 9. The stabilizing mechanism operates in conventional manner and requires no detailed description for an understanding of the present invention.

The operators station 7 in front of the grain bin 8 as shown in FIGS. 1 and 2 comprises a floor plate 34 which is supported on laterally spaced forwardly projecting beam members of the vehicle frame 6. As usual, the floor plate 34 is located at a substantial elevation above the ground and includes a generally horizontal main part and a forwardly and upwardly inclined front portion. An operators seat 36 is mounted at the station in the conventional manner, and the usual controls at the station include a steering unit 37 mounted on railing 40, andv foot pedals 38 mountedadjacent the upwardly inclined forward portion of the floor plate 34.

Access to the operators station 7 from the ground is afforded by means of a ladder arrangement at the mounting side of the machine and which includes an up and down movable ladder 39. A quadrilateral articulated supporting structure for the ladder 39 comprises an upper pair of laterally spaced angle iron beams 41 and 42 (FIGS. 2 and 4), and a lower pairof laterally spaced angle iron beams 43 and 44 below the beams 41 and 42, respectively. As best shown in FIG. 3, the

beam elements 41 and 42 are pivotally connected with the vehicle body adjacent the operators station 7 by means of pivot'pins 46. and 47, respectively; and the laterally spaced beam elements 43 and 44 are similarly mounted on the vehicle body in proximity to the operators I station 7 by pivot pins 48 and 49, respectively. Referring to the enlarged View of FIG. 6, an angle iron bracket 51 is secured, as by welding, to a supporting beam 52 for the floor plate 34 in depending relation thereto, and the pivot pin 46 is nonrotatably secured in a boss 53 of the angle iron bracket 51 by means of a set screw 54. The beam element'41 has a bearing 56 on the pivot pin 46 and is retained on the pin '46 by means of a cotter pin 57 extending through a hole in the free end of the'pin 46. The lower beam element '43 is similarly mounted on the bracket 51 below the pivot pin 46 by means of a pivot' pin 48 which is secured in a boss 59 of the bracket 51 by a set screw 61. The pin 48 extends through a hearing 62. of thebeam element 43. and a cotter pine63. is mounted in the free end of the pin '48.

I The foregoing explanations withrespect to the mount-- ing. of the beam elements 41 and 43 on the main body similarly apply to the mounting ofthe beam elements 42 and 44 as shown in FIG. 3. The pivot pins 46 and,

47 for the upper pair of beam elements 41 and 42 are aligned on a common axis which extends longitudinally of the vehicle body, and the pivot pins 48 and 49 are similarly aligned on a common axis which extends longitudinally of the vehicle. body and below the common axis of the pivot pins 46 and 47. i v

The outer ends of the beams elements 41 and '43 are pivotally connected to an upright plate member 64, as shown in FIG. 2, and the outer ends of the beam elements 42 and 44 are pivotally connected to a similar 4 66, respectively. The beam elements 43 and 44 similarly mount pivot pins 69 and 71, respectively, which are rotatably received in bearing apertures of the vertical plates 64 and 66, respectively. The plate members 64 and 66 extend outwardly beyond the outer ends of-the upper and. lower beam assemblies 41, ,42 andv 43,/44, respectively, and they are rigidly securedat their outer ends, as bywelding, to side members 72 and 7 3, respec tively (FIG. 1), of the ladder 39. The transverse space between the plate members 64 and 66 is occupied by a plate metal structure which has an upper portion 74, a

lower portion 76 and riser portion 77. The upper plate as by Welding, at their opposite sides withthe plate members 64yand 66, respectively, and the lower plate portion 76 extends parallel to the upper plate portion 74 and is rigidly connected at its outer end, as by. welding, with the side members 72 and' 73 of the ladder 39. Below the plate member 76 the side members 72 and 73 of the ladder 39 are connected With'each other by steps 78, 79 and 81. V

. Secured to the upper end of the ladder side member 72 and to the side plate 64, asshown in FIG. 2, is a first arched rail member 82. A second straight rail member 83 is pivotally connected at 84 with an upper end of the rail member 82,'and the other end of the second rail member 83 is pivotally connected as 86 with the railing structure 40 of the operators station 7. In FIG. 8 the upper part of the'rail member 82 shown in FIG. 2 is broken away to expose another arched rail member 89 which is a duplicate of the arched rail member 82 and which is secured to the side member 73 of'the ladder 39 (FIG: 1) and to the plate 66 (FIG. 5). The upper end of the arched rail member 89 is pivotally connected at 90 (FIG. 8) with another rail member 95 which corresponds to .therail member 83 (FIG. 2). As. shown in FIG. 3, a vertical frame member 92 of the vehicle body mounts 1 a pivot pin 91 in axial alignment with the pivotal connection 86, and the rail member 95 which corresponds to the rail member 83 is pivoted at 91 to the frame member 92.

In order to accommodate up and down movement of the ladder relative to the vehicle body as illustrated by FIGS. 8 and 9, the vertical spacing of the pivot pins 84 and 67 at the arched rail member 82 (FIG. 2) is the same asthe vertical spacing of the pivot pins 86 and 46 on the vehicle body. Similarly, the vertical spacing of the pivot pins 90, 68 at the arched rail member 89 (FIGS. 7 and 8) is the same as the vertical spacing between the pivot pins 91, 47 (FIG. 3) on the vehicle body.

Referring to FIGS. 2 and 4, an intermediate step member is mounted on the beam elements 41, 42 and 43, 44 between the operators station 7 and the end step assembly 74, 76, 77. The intermediate step member comprises a side plate 93 (FIG. 4) adjacent the inner sides of the beam elements'41, 43, a side plate 94 adjacent the inner sides of the beam elements 42 and 44, and a cross plate 96 which is secured along its opposite sides, as by welding, to the plates 93 and 94, respectively. Pivot pins 97 and 98 on a common 'axis connect the intermediate step assembly 93, 94, 96 with the side beams 41 42, respectively, and a cross shaft 99 connects the intermediate Y step assembly with the side beams 43 and 44, as shown in I step members, and the supporting structure, for the wheel plate member 66 as shown in FIG. 7. Pivot pins 67 and 68 are fixedly mounted on the beam elements 41"and 42, respectively, and are rotatably received 'in' axially 12 comprising the axle beam 14, wheel carrier 22 and guide link 27. As shown in FIG. 4, the upper ends of "the side bars 101 and 192. are pivotally mounted on the cross shaft 99, and the lower ends of the side bars 101- ateaae and 102 are pivotally mounted on a cross shaft 103 which is mounted on the guide link 27. The cross shaft 103 extends through a mounting sleeve 104 which extends transversely of the guide link 27 and is rigidly secured thereto by means of retainer clips 106 and 107 welded to the sleeve 104 and to the guide link 27.

FIG. 2 illustrates the position of the ladder 39 rela tive to the vehicle body when the supporting wheels 11 and 12 rest on level ground. In this position of the ladder the distance A from its lower end to the ground affords ample clearance fortravel of the combine on level ground, but it is nevertheless short enough so that an operator wishing to ascend from the ground to the operators station 7 may conveniently reach the lowest step 81 of the ladder.

FIG. 8 illustrates the position of the ladder 39 relative to the vehicle body when the supporting wheels 11 and 12 rest on laterally sloping ground which extends downhill at the mounting side of the combine. In order to keep the vehicle body upright, the wheels 11 and 12 are raised and lowered, respectively, by actuation of the hydraulic cylinders 32 and 33, and downward movement of the wheel 12 relative to the vehicle body as illustrated by FIG. 8 is transmitted through the link assembly 101, 102 to the articulated ladder support comprising the upper pair of side beams 41, 42, the lower pair of side beams 43, 44, the end step assembly 74, 76, 77, and the intermediate step assembly 93, 94, 96. Downward movement of the link assembly 101, 102 by downward movement of the wheel support at the mounting side of the combine causes downward swinging movement of the articulated ladder support on the fixed axes of the pivot pins 46, 47 and 48, 49, and translatory downward movement of the ladder 39 together with. the arched rail members 82 and 89. During such translatory downward movement of the ladder the rail members 83 and 95 remain parallel to the beam members 41 and 42. It will also be noted that the downward swinging movement of the articulated ladder support causes translatory downward movement of the intermediate step assembly relative to the vehicle body.

The plate member 96 of the intermediate step assembly and the plate members 74 and 76 of the end step assembly remain parallel to the platform 34 during up and down movement of the ladder 39 relative to the vehicle body. I

FIG. 9 illustrates the position of the ladder39 when the supporting wheels 11 and 12 of the combine rest on laterally sloping ground which extends uphill at the mounting side of the combine. Upward adjustment of the wheel 12 relative to the vehicle body by operation of the hydraulic cylinders 32 and 33 is transmitted from the axle structure 14, 22, 27 through the link structure 101, 102 to the cross shaft 99 (FIG. 4) and causes translatory upward movement of the ladder and associated step plates 74, 76 and 96 relative to the vehicle body.

The geometry of the motion transmitting linkage between the support for the wheel 12 and the articulated ladder support is such that downward movement of the wheel support relative to the vehicle body causes downward movement of the ladder 39 not only relative to the vehicle body but also relative to the wheel 12. Conversely, upward movement of the same wheel support causes upward movement of the ladder 39 not only relative to the vehicle body but also relative to the wheel 12. In other words, the swinging movement of the articulated ladder support about the axis of the fixed pivot axes on the vehicle body is controlled by accelerated motion transmitting means which are operatively interposed between the support for the wheel 12 and the ladder so as to raise and lower the ladder relative to said wheel support in response to up and down movements, respectively, of said wheel support relative to the vehicle body.

As shown in FIG. 8, the lower end of the ladder 39 is spaced a distance B from the downwardly sloping 6 ground which is short enough to aiford convenient access to the lowest step 81 of the ladder from the sloping ground at the mounting side of the vehicle. The mentioned downward movement of the ladder relative to the wheel 12 under the conditions illustrated by FIG. 8 is desirable in order to present the lowest step of the ladder at a convenient height for access from downhill sloping ground at the mounting side of the vehicle.

In FIG. 9 the lower end ofthe ladder 39 is raised relative to the wheel 12, as compared with the condition of the parts as shown in FIG. 2, and such raising of the ladder end relative to the wheel 12 is desirable in order to maintain proper clearance between the lower ladder end and the upwardly sloping ground at the mounting side of the combine.

In general terms, the herein disclosed ladder mounting comprises a ladder support, as represented by the parallelogram structure 41, 42 and 43, 44 and associated parts, which is swingably mounted on the vehicle body for selective adjustment to either a generally horizontal position (FIG. 2) in outwardly extending relation to the vehicle body, or to raised and lowered positions (FIGS. 9 and 8) in upwardly and downwardly inclined relation, respectively, to said horizontal position. The ladder support including beams 41, 42, 43 and 44, and plate members 64, 66, and the ladder 39 are constructed, mounted and arranged so that adjustment of the ladder support to horizontal, raised and lowered positions will be effective to present the lower end of the ladder 39 in upwardly spaced relation to level, uphill and downhill ground traversed by the combine, as illustrated by FIGS. 2, 9 and 8, respectively. Thrust transmitting means as represented by the link assembly 101, 102 are operatively interposed between an up and down movable wheel support at the mounting side of the combine, and an articulated parallelogram structure which supports the ladder. In the illustrated embodiment of the invent-ion, side members of such a parallelogram structure are represented by the upper pair of beam members 41, 42, by the lower pair of beam members 43, 44, and also by the pair of second rail members 83, 95, any one of which pairs cooperates with any of the others to eifect translatory up and down movement of the ladder relative to the vehicle body.

The wheels 12 and 11 represent first and second ground engaging wheels which support the axle structure 14, 21, 22, 24, 27 at one side and the other, respectively, of the vehicle body; and the parallelogram type ladder support, its connection with the axle structure by means. of the link assembly 101, 102, and the ladder 39 areconstructed, mounted and arranged so as to present the lower end of the ladder in upwardly spaced relation to the point of ground contact of said first wheel 12, as illustrated by the double headed arrows A and B in FIGS. 2 and 8.

As shown in FIGS. 2, 8 and 9, the articulated parallelogram structure or quadrilateral ladder support extends laterally outward from the vehicle 'body in overlying relation to the supporting wheel 12 at the mounting side of the combine, and the ladder 39 is mounted on and extends downwardly from said ladder support at the axially outer side of the wheel 12.

While in the foregoing a preferred embodiment of the invention has been disclosed it should be understood that it is not intended to limit the invention to the particular forms and details described hereinabove, and that a the invention includes such other forms and modifications as are embraced by the scope of the appended claims.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

1. In a vehicle of the hillside combine type, the combienemas operators platform, and a connecting. member having ing. member; and actuating means operatively connected with said parallelogram structure for swingingthe latter about said pivot axes on said vehicle body; said parallelogram structure, connecting member, ladder and actuating means being constructed, mounted and arranged so as to present the lower end of said ladder in upwardly spaced relation to level, uphill and downhill ground traversed by said vehicle. i

2. In a vehicle of the hillside combine type, the combination of a vehicle body, a wheel supportrand an access ladder mounted independently of each other on said vehicle body for up and down movement relative thereto, and actuating means for said ladder operatively connected with said wheel support so as to raise and lower said ladder relative to said vehicle body in response to up' and down movements, respectively, of said wheel support relative to said vehicle body; said ladder and actuating means being constructed, mounted and arranged so as to present the lower end of said ladder in upwardly spaced relation to the ground traversed by said vehicle.

3. In a vehicle of. the hillside combine type, the combination of a vehicle body, a wheel support and an access ladder mounted independently of each other on said vehicle body forup and down movement relative thereto, and accelerative motion transmitting means operatively interposed between said wheel support and said ladder so as to raise and lower said ladder relative to said wheel support in response to up. and down movements, respectively, of said wheel support relative to said vehicle body. 7 4. In a vehicle of the hillside combine type, the combination of a vehicle body, running gear including an up and down movable wheel support, a ladder support'swing- .able on said vehicle body between raised and lowered positions in later-ally outward extending relation thereto, actuating means for said ladder support operatively connected with said wheel support; and a ladder swingably mounted on said ladder support in depending relation thereto; said ladder support, actuating means and ladder and down movable wheel support, a ladder support swingably connected with said vehicle body on an axis extending longitudinally of the latter in elevated relation to said wheel support, thrust transmitting means operatively interposed between said wheel support and said ladder support,'a ladder pivotally connected withsaid ladder support, a first rail member rigidly connected with said ladder in upwardly extending relation to said ladder support, and a second rail member having opposite ends pivotally connected, respectively, with said first rail member and with said vehicle body in'elevated relation to said ladder support; said ladder support, thrusttransmitting means and ladder being constructed, mounted and arranged so as to present the lower end of said ladderfin upwardly spaced relation to the ground traversed. by said vehicle vehicle body and extending laterally outward therefrom in overlying relation to said supporting wheel; a connecting member extending transversely between one pair of said laterally spaced. beam elements and pivotally connected therewith at its opposite sides, respectively; pivot means at said opposite sides of said connecting member. pivotally connecting the latter with the other pair of saidlaterally spaced beam elements; a ladder rigidly connected with said connecting member; and link means connecting said supporting wheel in upward and downward thrust transmitting relation with one pair of said laterally spaced beam elements.

10. In a vehicel of the hillside combine type, the combination of a vehiclebody; running gear including an up being constructed, mounted and arranged so as to present 7 the lower end of said ladder in upwardly spaced relation to the ground traversed by said vehicle.

5 In a vehicle of the hillside combine type, the combination of a vehicle body, running gear including an up and down movable wheel support, an articulated quadrilateral ladder support having parallel upper and lower pivot axes on said vehicle body, thrust transmitting means operatively interposed between said wheel support and said ladder support, and a ladder operatively mounted on said ladder support for up and down movement thereby relative to said vehicle body; said ladder support, thrust transmitting means and ladder being constructed, mounted and arranged so as to present the lower end of said'ladder in upwardly spaced relation to the ground traversed by said vehicle.

6. In a vehicle-of the hillside combine type, the combination of a vehicle body, running gear including. an up and down movable ground engaging supporting wheel, an

. the axially outer side of said wheel; said ladder support,

link means and ladder being constructed, mounted and arranged so as to present the lower end of said ladder in upwardly spaced relation to the point of ground contact of said wheel.

7. In a vehicle of the hillside combinetype the combiand down movable wheel support; an articulated parallelogram structure above said wheel support having upper and lowerpivot axes fixed on and extending longitudinally of said vehicle body, a linkstructure pivotally connected at opposite ends thereof with said wheel support and with said parallelogram structure on lower and upper axes, respectively, extending parallel to said fixed pivot axes, and a ladder mounted on said parallelogram structure for translatory up and down movement thereby and having a lower end in upwardly spaced relation to the point of ground contact ofsaidsupporting wheel.

11, In a'vehicle of the hillside combine type, the combination set forth in claim 10, and step means between said ladder and vehicle body mounted on said parallelogram structure for translatory movement thereby relative, to said vehicle body. i

12. In a vehicle of the hillside combine type having a vehicle body including an elevated operators station, a transversely extending axle structure in underlying relation to said operators station and rockably connected at its center with said vehicle body, and first and second ground engaging wheels supporting said axle structure at "ladder operatively mounted on said parallelogram structure for translatory up and down movement thereby relative to said vehicle body and terminating at its lower end in upwardlyspaced relation to the point of ground contact of said first ground engaging wheel.

. 3- e m inat pn e fa s n la m 2 wh n s d ladder is mounted on said parallelogram structure so as to depend therefrom at the axially outer side of said first ground engaging supporting wheel, and wherein said supporting link is operatively 'connected with said parallelogram and axle structures so that said ladder will be raised and lowered relative to said supporting wheel upon up and down movement, respectively, of said supporting wheel relative to said vehicle body.

References Cited in the file of this patent UNITED STATES PATENTS Snyder Dec. 29, 1903 Gohlke July 29, 1913 Bailey Jan. 23, 1934 I Home Sept. 12, 1961 FOREIGN PATENTS Great Britain of 1876 

1. IN A VEHICLE OF THE HILLSIDE COMBINE TYPE, THE COMBINATION OF A VEHICLE BODY INCLUDING AN OPERATOR''S PLATFORM; AN ARTICULATED PARALLELOGRAM STRUCTURE COMPRISING AN UPPER AND A LOWER BEAM ASSEMBLY HAVING PARALLEL, UPPER AND LOWER PIVOT AXES, RESPECTIVELY, IN FIXED, LENGTHWISE EXTENDING RELATION TO SAID VEHICLE BODY AND ADJACENT TO SAID OPERATOR''S PLATFORM, AND A CONNECTING MEMBER HAVING UPPER AND LOWER PIVOT CONNECTIONS WITH SAID UPPER AND LOWER BEAM ASSEMBLIES ON UPPER AND LOWER AXES, RESPECTIVELY, EXTENDING PARALLEL TO SAID FIXED UPPER AND LOWER PIVOT AXES; A LADDER RIGIDLY CONNECTED WITH SAID CONNECTING MEMBER; AND ACTUATING MEANS OPERATIVELY CONNECTED WITH SAID PARALLELOGRAM STRUCTURE FOR SWINGING THE LATTER ABOUT SAID PIVOT AXES ON SAID VEHICLE BODY; SAID PARALLELOGRAM STRUCTURE, CONNECTING MEMBER, LADDER AND ACTUATING MEANS BEING CONSTRUCTED, MOUNTED AND ARRANGED SO AS TO PRESENT THE LOWER END OF SAID LADDER IN UPWARDLY SPACED RELATION TO LEVEL, UPHILL AND DOWNHILL GROUND TRAVERSED BY SAID VEHICLE. 